The present invention relates to a recording medium in the form of a tape cassette containing a magnetic tape, a tape drive apparatus capable of recording and/or reproducing information to and/or from the tape cassette, and a recording and/or reproducing method for use with the tape drive apparatus.
Tape streamer drives are a well-known drive apparatus for recording and reproducing digital data to and from a magnetic tape serving as a recording medium held in a tape cassette. Depending on the tape length of the tape cassette they use, some tape streamer drives can record large quantities of data amounting to tens to hundreds of gigabytes. Their mass storage capability allows the tape streamer drives to be utilized extensively in diverse applications including the backup of data recorded illustratively on hard discs in the computer body and the storage of picture data and other massive data.
In a data storage system made up of such a tape streamer drive and a tape cassette containing a magnetic tape, management information or the like is needed for the drive to manage appropriately its recording and/or reproduction of data to and/or from the magnetic tape. The management information includes information about diverse locations on the magnetic tape as well as a use history of the tape.
A management information area is located at the beginning of the magnetic tape or at the beginning of each of the partitions formed along the tape. Before writing or reproducing data to or from the magnetic tape, the tape streamer drive gains access to the management information area to read necessary management information therefrom. Based on the management information thus retrieved, the tape streamer drive performs various processes allowing subsequent recording or reproducing operations to proceed appropriately.
At the end of the data recording or reproduction of data, the tape streamer drive again accesses the management information area to update the relevant information therein in a manner reflecting any changes resulting from the preceding recording or reproducing operation. The updates are carried out to prepare for the next recording or reproducing operation. Thereafter, the tape cassette is unloaded and ejected from the tape streamer drive.
Where recording and/or reproduction is performed on the basis of such management information, the tape streamer drive is required twice to access the management information area at the beginning of the magnetic tape or of one of its partitions, first, before the operation is started, and later, when the operation has ended, so that the relevant data should be written to and read from the area each time. In other words, the tape cassette cannot be loaded or unloaded halfway through the recording or reproducing operation along the magnetic tape.
Upon access to the management information area, the tape streamer drive is required physically to feed the magnetic tape. That means it takes some time to access the beginning of the magnetic tape or of one of its partitions. In particular, if the recording or reproducing operation on the magnetic tape ends at a considerable physical distance from the management information area, it takes a correspondingly long time to feed the tape before the target area can be reached.
As described, data storage systems that utilize tape cassettes as their recording media require a relatively long access time before a single write or read operation is completed, i.e., from the time the magnetic tape was loaded until it is unloaded. It is obviously preferable to minimize the time required for such a series of access-related operations.
For that purpose, techniques have been proposed whereby a nonvolatile memory is installed within a tape cassette enclosure so that the memory may accommodate management information (refer illustratively to Japanese Patent Laid-open No. Hei 9-237474). The tape streamer drive for use with such a memory-equipped tape cassette incorporates an interface for writing and reading management information to and from the nonvolatile memory, i.e., information about the recording and reproduction of data to and from the magnetic tape.
The above arrangement eliminates the need illustratively to rewind the magnetic tape at the time of loading or unloading the cassette. That is, the tape cassette may be loaded or unloaded halfway through the ongoing operation along the tape.
As described, the nonvolatile memory is attached to the tape cassette to shorten access time and gain other benefits. As long as the tape cassette is normally used, the content of data placed in the nonvolatile memory is generally kept consistent with the initial purpose of the tape cassette and with its past history of write and read operations made thereto and therefrom.
Typically, the above-described nonvolatile memory for the tape cassette is secured mechanically inside the cassette enclosure. That means it is impossible to exclude the possibility that the initially installed nonvolatile memory might be removed from within the enclosure and replaced by an illicit nonvolatile memory.
Described below is a concrete example of how the tape cassette can be tampered with. In addition to the normal-type tape cassette for normal data storage, there have been developed and marketed tape cassettes intended for special uses. A tape cassette for one of such special uses is illustratively designed to have a magnetic tape to which data can be recorded only once. Once recorded on the tape, the data can only be read and cannot be overwritten. This tape cassette feature is called WORM (Write Once Read Many). The WORM feature is also provided to disc type recording media such as CD-Rs and DVD-Rs.
On a WORM tape cassette, data can only be read from the data-recorded areas and no data can be written thereto. History information about the read and other operations on the tape cannot be updated in a manner causing any management information area associated with the recorded areas to reflect the past changes. Such history information can only be written to the nonvolatile memory in the tape cassette. Therefore, the management information that needs to be consistent with the WORM tape cassette is always stored into its nonvolatile memory. Where the WORM tape cassette is subject to the recording and/or reproduction of data, it is mandatory to use the management information held in the nonvolatile memory of the cassette and not any management information recorded on the magnetic tape.
Suppose now that a malicious user has illicitly replaced the original nonvolatile memory of the WORM tape cassette and that the memory does not contain any information designating the WORM feature but information designating only a normal type tape cassette. In that case, the tape cassette originally designed to provide the WORM feature will be recognized as a normal type tape cassette if the designating information in the nonvolatile memory is referenced as the basis for the recognition. This will enable attempts to write data even to the recorded areas on the tape. That is, data can be falsified or otherwise corrupted on the tape in the cartridge.
Illustratively, WORM tape cassettes are actually utilized most often for the recording of important data that call for secure measures to maintain their high storage value, given the premise that recorded data can only be read and neither overwritten nor erased. Hence high levels of security are demanded by and offered to the data accommodated by the WORM tape cassette, so that the data will not be destroyed or falsified on the magnetic tape inside.
The fraudulent case above involving the WORM tape cassette is but one example of tape cassette tampering. Regardless of their intended purposes, nonvolatile memory-equipped tape cassettes could have their data destroyed or corrupted on the magnetic tape if their memories were illicitly replaced.
In actually marketing nonvolatile memory-equipped tape cassettes, tape cassette vendors are required to provide a scheme for preventing cases of tampering such as illegal replacement of the nonvolatile-memory.